Field of the Invention
The present invention relates to a metal separator for fuel cells and a manufacturing method thereof. In detail, it relates to a metal separator for fuel cells on which a surface treatment had been conducted, and a manufacturing method thereof.
Related Art
In recent years, fuel cells that generate electric power by allowing reactant gases to undergo an electrochemical reaction have received attention as a novel source of power for automobiles or the like. Fuel cells are said to be preferable in the aspect of the electric power generation efficiency being high due to directly obtaining electricity by way of an electrochemical reaction. In addition, fuel cells are said to be preferable also from the aspect of the impact on the environment due to only producing harmless water during electric power generation.
For example, solid polymer-type fuel cells have a stack structure in which several tens to several hundreds of cells are layered. Each cell is configured by sandwiching a membrane electrode assembly (MEA) with a pair of separators. The membrane electrode assembly is configured by an anode and cathode as well as an electrolyte membrane sandwiched between these electrodes, and both electrodes include a catalyst layer that contacts the electrolyte membrane, and a gas diffusion layer that contacts the catalyst layer. In addition, fuel gas channels are formed in the separator on one surface thereof, and oxidant gas channels are formed on the other surface.
With the solid polymer-type fuel cell provided with the above such configuration, hydrogen is supplied as fuel gas through the fuel gas channels to the anode. In addition, air is supplied as oxidant gas through the oxidant gas channels to the cathode. Then, the hydrogen supplied to the anode is protonated on the catalyst layer, and the yield protons migrate through the electrolyte membrane to the cathode. At this time, electrons yielded along with protons are drawn to an external circuit and employed as electrical energy.
However, metal separators made of stainless steel or the like are usually employed as the above-mentioned separators. Various surface treatments have be known to be conducted on this metal separator such as conducting a water-repellent treatment with the purpose to suppressing the occurrence of flooding, and a plating process with the purpose of suppressing oxidation to suppress an increase in the contact resistance with the membrane electrode assembly. For example, a technology has been disclosed in which, after forming a resin layer on the surface of the metal separator, a water-repellent layer is formed in an island form on this resin layer (refer to Patent Document 1).
[Patent Document 1] Japanese Unexamined Patent Application, Publication No. 2007-141819